Make item filtering functionality more intuitive

[davidmcclure]

Item filtering has some odd behavior that I do not totally understand. Right now, when the All / None option is toggled, the code retrieves all items no matter what, and they all display. But, if you start filtering down the list - say, uncheck a single tag - the code then branches differently and just retrieves items that fall into one of the checked buckets (one of the tags, types, or collections).

Then, though, if you re-check the item that you unchecked, the full list of items does not reappear in its entirety (since the code is still checking for membership in the groups individually and not fetching all regardless of membership, as it would if the All / None were toggled). It is as if there are some items that are not selected when the code fetches all items that appear in any extant tag, collection, or type, which seems to be impossible. Theoretically, getting all items of all extant types should get all items, but it doesn't.

Either way, the behavior of the server code here is not intuitive, and the UX for the filterer should be improved.

[davidmcclure]

Since I expect that the filtering functionality will be used mainly to apply 1 - maybe 2 - filters to the list of items (like, just show things with tag X) I think that the current implementation is sufficient. Also, since the all/none checkbox always allows the user to return the list to the full state, I think this is a non-issue.